1. Field of the Invention
This invention relates in general to a television receiver and particularly to a television receiver capable of receiving sound multiplex signals.
2. Description of the Prior Art
In the prior art, when a broadcast television signal having sound multiplex is recorded on a magnetic recording and/or reproducing apparatus such as a VTR (video tape recorder) and the signal reproduced therefrom is supplied to a television receiver two methods described as follows have been proposed. One of the methods provides that the reproduced signal from the VTR is directly supplied to the input stage of the video amplifier circuit of the television receiver and the reproduced audio or sound signals comprising the sound signals of the main sound channel and the subsound channel or left and right sound signals are supplied to the low frequency amplifier circuit of the television receiver. The second method provides that the reproduced signal is modulated so that it is in the same form as the broadcast signal which is then supplied to the high frequency input stage of the television receiver.
In the first method, it is necessary to electrically isolate the magnetic recording and/or reproducing apparatus from the television receiver with the use of a coupling device such as a transformer, a photo-coupler or other simiar device. In this method, the coupling device for three systems are required and, thus, the former method is expensive and the cost becomes about equivalent wherein a television receiver and a reproducing apparatus are installed.
According to the second method, since the sound signal must be multiplied, especially the modulating processing circuit in the sound signal system becomes complicated and expensive which makes such system not so desirable.